Prior to inspecting the integrity of a pipeline with a pig it is usually necessary to first clean the pipeline to remove debris from the pipeline that would otherwise interfere with the inspection instrumentation of the pig. In some instances the pipeline may not have been cleaned for 10, 15 or 20 years, however, in view of recent regulations older pipelines are now being required to be cleaned and inspected. The debris typically comprises dust, grease and sludge built up over years of use of the pipeline. In instances where the pipeline has never been cleaned for inspection, it is common to find devices, scrap metal and other waste left in the pipeline by laborers who built the pipeline.
In practice, the cleaning device, or cleaning pig, scrapes the inside wall of the pipeline. The cleaning device typically carries metal brushes for scraping the pipeline and magnets for collecting metal debris. The cleaning device has a propulsion unit that seals with the internal wall of the pipeline and pushes all other scraped debris in front of the cleaning device as the device moves through the pipeline. In pipelines designed for a cleaning device, the cleaning device pushes the debris to an entry/exit hatch in the pipeline where the debris is removed by shovel.
This cleaning device, which pushes the debris in front of it, typically comprises either a foam pig that seals against the pipeline inner wall, or a dome shaped disk of predetermined diameter that seals against the pipeline inner wall. The foam pig and disk like device is propelled by media in the pipeline acting against an upstream face of these cleaning devices. For a pipeline having multiple diameters along its length, the dome shaped disk cleaning device is modified with a series of butterfly rubber flaps attached about the periphery of the disk. These flaps are resilient and are sprung outwardly to contact the interior wall of the pipeline when the diameter of the pipeline becomes larger than the predetermined diameter of the dome shaped disk. These flaps, like the dome shaped disk outer periphery, make contact with the internal wall of the pipeline at an acute angle. This angle of contact does not provide an effective scraping edge surface to effectively remove debris from the internal wall of the pipeline.
To accommodate for the cleaning of pipelines not designed with exit/entry hatches for a cleaning device, it is necessary to create “hot taps” in the pipeline spaced apart by distances of many miles. The hot taps usually each comprise a Y connection with the pipeline that allows for the cleaning device to be inserted in the pipeline at a tight angle of about 45 degrees. Launching the cleaning device is not a problem. The problem for the cleaning device comes when the device is to be removed from a downstream Y connection hot tap. The device must once again negotiate a tight angle of 45 degrees to exit the hot tap. However, there is no way of knowing how much debris is being pushed by the cleaning device and should this debris clog the pipeline at the hot tap exit, the cleaning device may become stuck in the pipeline.
Accordingly, there is a need for a cleaning device for use in a pipeline that is not prone to problems associated with a cleaning device that pushes the debris out in front of the cleaning device as the device moves along the pipeline, or to pipelines containing unmanageable amounts of debris.